The present invention relates to the manufacture of glass fittings, and more particularly to methods of manufacturing glass fittings with side channels.
Such fittings can be used in various branches of industry and agriculture, wherein glass pipelines are used.
At the present time, fittings for glass pipelines are manufactured by three methods:
1. Blowing in a split mold.
2. Welding of separate pipe segments (gas welding or, less often, electrical welding).
3. Profile bending of a preheated rectilinear pipe blank.
The first process is manual, while the second and the third are mechanized.
Two types of pipes and shaped pieces for glass pipelines are manufactured: with flat edges and with beads.
In manufacturing fittings according to the second and third methods, manufacturers fabricate the pipes, cut them into measured segments, heat and weld these segments to one another, anneal them, and cut the ends of the side channels to size.
Manufacturing of fittings with beads involves the following additional operations: pressing off the beads, annealing them and removing the treatment allowance, heating the fitting and the beads, welding the beads to the branch pipes of the fitting, annealing the whole article with the beads, and grinding the end faces of the side channel.
These operations are additional to those normally involved in all the three methods mentioned above.
About 15 operations are required to manufacture fittings with beads.
All these three methods involve a high percentage of rejects at all process steps, as well as during hydraulic impact and thermal resistance tests.
There are also known other methods of manufacturing glass fittings. Thus, for example, a method has been tested of pressing T-bends with a movable vertical plunger and a fixed horizontal one. In this method, the molten glass being molded travels all the way along intricate paths of different length, whereby part of the molten glass intended for molding of a side branch pipe prematurely solidifies.
Also known is a method of molding glass fittings with side channels for branch pipes, wherein the molding of the coaxial channels is achieved by pressing with a vertically moving plunger provided with a following-and-retracting bottom plate, while the side channels are made by vacuum molding with subsequent blowing with compressed air from within through the cavity in the moving plunger die.
These methods are carried out with a mold wherein at least one of the channels is a vertical one.
The above methods have not found industrial application due to the fact that the combination of pressing, vacuum molding and blow molding of the rapidly cooling molten glass being molded in different positions in the mold has failed to provide for the required geometrical configuration of the articles.
The articles were undermolded, oval in shape, misaligned, differing in wall thickness, etc. In addition to the above disadvantages, the currently used methods of manufacturing glass fittings are also deficient in the following: multistep process, wide dimensional variations, formation of folds and considerable difference in the wall thickness after profile bending, gas bubbles in the welded seams, appearance of heavy stresses in various parts of an article during welding, necessity of grinding the end faces due to the axial misalignment of the side channels and perpendicular misalignment of the end faces, additional operations of making beads and welding them to the end faces of the side channels of the fittings with subsequent additional annealing, etc.
Thus, the above methods involve too many process steps and a great number of manual operations with low output of quality products and, consequently, high unit cost of manufacture.